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Plant Physiol. 1976 May; 57(5): 780–788.
PMCID: PMC542117

Lipoxygenase and Hydroperoxide Lyase in Germinating Watermelon Seedlings 1


Lipoxygenase (EC was found in seedlings of Citrullus lanatus (Thunb.) Matsum. and Nakai (watermelon). The enzyme has pH optima of 4.4 and 5.5 and is inhibited by 0.2 mM nordihydroguaiaretic acid. It is present in two functional units with estimated molecular weights of 120,000 and 240,000, respectively.

A new enzyme, tentatively termed hydroperoxide lyase, has been partially purified from watermelon seedlings. The enzyme, located principally in the region of the hypocotyl-root junction, catalyzes the conversion of 13-l-hydroperoxy-cis-9-trans-11-octadecadienoic acid to 12-oxo-trans-10-dodecenoic acid and hexanal. The hydroperoxide lyase enzyme from watermelon has a molecular weight in excess of 250,000, a pH optimum in the range of 6 to 6.5, and is inhibited by p-chloromercuribenzoic acid. Its presence has also been demonstrated in other cucurbits.

The maximum activity of both enzymes occurs on the 6th day of germination. The identification of the products of the hydroperoxide lyase reaction suggests that lipoxygenase and hydroperoxide lyase may be involved in the conversion of certain polyunsaturated fatty acids to traumatic acid (trans-2-dodecenedioic acid).

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.
  • Esselman WJ, Clagett CO. Products of linoleic hydroperoxide-decomposing enzyme of alfalfa seed. J Lipid Res. 1974 Mar;15(2):173–178. [PubMed]
  • Gardner WH. Sequential enzymes of linoleic acid oxidation in corn germ: lipoxygenase and linoleate hydroperoxide isomerase. J Lipid Res. 1970 Jul;11(4):311–321. [PubMed]
  • Hamberg M. Decomposition of unsaturated fatty acid hydroperoxides by hemoglobin: Structures of major products of 13L-hydroperoxy-9,11-octadecadienoic acid. Lipids. 1975 Feb;10(2):87–92. [PubMed]
  • Kolattukudy PE, Croteau R, Walton TJ. Biosynthesis of Cutin: Enzymatic Conversion of omega-Hydroxy Fatty Acids to Dicarboxylic Acids by Cell-free Extracts of Vicia Faba Epidermis. Plant Physiol. 1975 May;55(5):875–880. [PMC free article] [PubMed]
  • LOWRY OH, ROSEBROUGH NJ, FARR AL, RANDALL RJ. Protein measurement with the Folin phenol reagent. J Biol Chem. 1951 Nov;193(1):265–275. [PubMed]
  • Rahn CH, Schlenk H. Detection of aldehydes with 4-amino-5-hydrazino-1,2,4-triazole-3-thiol as spray reagent. Lipids. 1973 Nov;8(11):612–616. [PubMed]
  • Zimmerman DC, Vick BA. Hydroperoxide isomerase: a new enzyme of lipid metabolism. Plant Physiol. 1970 Sep;46(3):445–453. [PMC free article] [PubMed]
  • VIOQUE E, HOLMAN RT. Characterization of the ketodienes formed in the oxidation of linoleate by lipoxidase. Arch Biochem Biophys. 1962 Dec;99:522–528. [PubMed]
  • Zimmerman DC. A new product of linoleic acid oxidation by a flaxseed enzyme. Biochem Biophys Res Commun. 1966 May 25;23(4):398–402. [PubMed]

Articles from Plant Physiology are provided here courtesy of American Society of Plant Biologists


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